In recent years, a greater emphasis has been placed on the use of insulation materials in dwellings or other structures to promote energy conservation and noise reduction. At the same time, innovative architectural designs have created a variety of shapes and sizes that do not always lend themselves to the use of a conventional fibrous batting, which is often available in rolls of uniform width. The conventional fibrous batting often fails to fully fill the space in which the batting is used. This has created a need for a technique for applying fibrous insulation that does not use uniform width batting.
This need has been fulfilled to a limited extent by developing various blown-in-place insulation techniques, wherein loose-fill fibrous insulation is blown into a cavity between the framing members of the wall, ceiling, or floor of a dwelling. The loose-fill insulation is capable of completely filling the cavity, regardless of its shape and size, thus effectively achieving a uniform volume of insulation for optimum energy conservation, as well as sound insulation purposes.
While blown-in-place insulation techniques have addressed insufficient fill problems inherent with insulation batting, one of the advantages of batting lost to blown-in-place insulation is the batting's ability to maintain insulation quality. This includes, of course, the density and thickness of the fibrous insulation, which is important to achieve a uniform thermal resistance. The thermal resistance of the insulation batting is often associated with a given “R-value”. When insulation batting is purchased, for example, to place in a new dwelling, it is often purchased by specifying a desired R-value. If installed in accordance with minimal prescribed installing techniques, the purchaser, due to uniform dimensions of insulation batting, can be count on at the insulation value having a certain thermal resistance.
When a blown-in-place insulation technique is employed, the advantage of controlling R-value associated with batting is lost. As a consequence, it is often necessary to also employ a technique for determining the density of the blown-in-place insulation for assuring that the insulation has the desired R-value.
Various techniques have been employed for the determining density in blown-in-place fibrous insulations. In one technique, a known mass of loose-fill is blown into a cavity. The volume of the filled cavity is measured. The mass is divided by the cavity volume to get density. A problem with this technique is that it slows down the installation process of the insulation and therefore, is not used. Moreover, it is difficult to calculate the actual volume of insulation that is blown into the cavity because there are so many features (i.e., windows, doors, devices, etc.) in the area that take up volume.
In another known technique, a space is first filled with blown-in-place insulation. Then, a sample of insulation of a known volume is removed from a wall cavity and weighed. Since the volume of the sample is known, it is possible to determine the density (i.e., weight per volume) of the insulation in the cavity. The R-value of the insulation may then be determined in a known manner simply by knowing the thickness of the insulation in the cavity. In some instances, the quantity of insulation may be loose or compressed. As a consequence, error in determining the density of the insulation can be magnified if care is not taken to correctly remove the sample or average a number of samples. This is also a very time consuming technique and consequently is often not practiced by insulation installers.
In yet another known technique, netting is secured to wall studs to enclose an underlying cavity. Insulation is blown into the cavity through a hole in the netting. The netting retains the insulation in the cavity. A bulging of the netting by the insulation in the cavity provides an indicator or signal when the cavity is filled with a sufficient amount of insulation. This technique is unreliable because it is based on the subjective observation of the insulation installers. Moreover, the mechanical properties of the netting material (e.g., the modulus of elasticity) affect the resiliency of the netting. In addition, mechanical properties of the insulation (e.g., the modulus of elasticity of the insulation, which is affected by the fiber diameter and the presence or absence of a binder) affect the resiliency of the insulation. Environmental conditions (e.g., humidity) may even affect the accuracy of the technique. Another disadvantage of this technique is that installers, in an effort to insure that a cavity is adequately filled, often overfill the cavity. Overfilling the cavity is undesirable because it causes the netting to bulge too much and wastes insulation. If the netting bulges too much, wallboard is difficult to install on the framing members. This has been recognized as a problem and thus has led to the use of a shield during installation, whereby the shield is held against the netting while the cavity is being filled to prevent the netting from bulging undesirably.
In view of the above techniques, it is apparent that there exists a need in the art for an improved apparatus and method for installing insulation that is blown into open wall cavities to a prescribed density wherein the improved apparatus and method provide increased accuracy.